Mechanism and regulation of circadian photoreception in the jewel wasp Nasonia vitripennis

The endogenous circadian rhythm exists in almost all organisms on Earth and is crucial for their foraging, reproduction, survival, and other biological activities. However, the molecular mechanisms behind circadian synchronization to the environment are poorly understood. Light is one of the most important environmental cues for circadian entrainment. In this thesis I investigated the circadian light photoreceptors and light input pathway of an insect, the jewel wasp, Nasonia vitripennis. A wide range of light, ranging from near UV to red light (390-650 nm), can entrain Nasonia’s daily rhythm. There are four visual photoreceptor classes present in Nasonia and at least three of these contribute to circadian photoentrainment with the environment. Different photoreceptors are not reinforcing but antagonizing each other, which may contribute to distinguishing between colours and contrasts. Although the same photoreceptors are involved in regulating diverse circadian behaviours, the underlying mechanisms appear different. I could confirm that the circadian light input pathway of Nasonia resembles more that of mammals than flies. Based on a transcriptomic analysis, I formed the hypothesis that light signals are conveyed by different neurotransmitters (glutamate and GABA) and several signalling pathways (CREB/CRE and AP-1 signalling) to the neurons (potentially clock neurons). The circadian clock is then reset through the induction of core clock genes (cry2 and npas2). Together, my findings explain the high light sensitivity in Nasonia and pave the way for further investigation of circadian timekeeping in insects.